After upgrading to MythTV 30 and MariaDB 10.3.18 on Debian buster, I noticed the following errors in my logs:

Jan 14 02:00:05 hostname mysqld[846]: 2020-01-14  2:00:05 62 [Warning] InnoDB: Cannot add field `rating` in table `mythconverg`.`internetcontentarticles` because after adding it, the row size is 8617 which is greater than maximum allowed size (8126) for a record on index leaf page.
Jan 14 02:00:05 hostname mysqld[846]: 2020-01-14  2:00:05 62 [Warning] InnoDB: Cannot add field `playcommand` in table `mythconverg`.`videometadata` because after adding it, the row size is 8243 which is greater than maximum allowed size (8126) for a record on index leaf page.

The root cause is that the database is using an InnoDB row format that cannot handle the new table sizes.

To fix it, I put the following in alter_tables.sql:

ALTER TABLE archiveitems ROW_FORMAT=DYNAMIC;
ALTER TABLE bdbookmark ROW_FORMAT=DYNAMIC;
ALTER TABLE callsignnetworkmap ROW_FORMAT=DYNAMIC;
ALTER TABLE capturecard ROW_FORMAT=DYNAMIC;
ALTER TABLE cardinput ROW_FORMAT=DYNAMIC;
ALTER TABLE channel ROW_FORMAT=DYNAMIC;
ALTER TABLE channelgroup ROW_FORMAT=DYNAMIC;
ALTER TABLE channelgroupnames ROW_FORMAT=DYNAMIC;
ALTER TABLE channelscan ROW_FORMAT=DYNAMIC;
ALTER TABLE channelscan_channel ROW_FORMAT=DYNAMIC;
ALTER TABLE channelscan_dtv_multiplex ROW_FORMAT=DYNAMIC;
ALTER TABLE codecparams ROW_FORMAT=DYNAMIC;
ALTER TABLE credits ROW_FORMAT=DYNAMIC;
ALTER TABLE customexample ROW_FORMAT=DYNAMIC;
ALTER TABLE diseqc_config ROW_FORMAT=DYNAMIC;
ALTER TABLE diseqc_tree ROW_FORMAT=DYNAMIC;
ALTER TABLE displayprofilegroups ROW_FORMAT=DYNAMIC;
ALTER TABLE displayprofiles ROW_FORMAT=DYNAMIC;
ALTER TABLE dtv_multiplex ROW_FORMAT=DYNAMIC;
ALTER TABLE dtv_privatetypes ROW_FORMAT=DYNAMIC;
ALTER TABLE dvdbookmark ROW_FORMAT=DYNAMIC;
ALTER TABLE dvdinput ROW_FORMAT=DYNAMIC;
ALTER TABLE dvdtranscode ROW_FORMAT=DYNAMIC;
ALTER TABLE eit_cache ROW_FORMAT=DYNAMIC;
ALTER TABLE filemarkup ROW_FORMAT=DYNAMIC;
ALTER TABLE gallery_directories ROW_FORMAT=DYNAMIC;
ALTER TABLE gallery_files ROW_FORMAT=DYNAMIC;
ALTER TABLE gallerymetadata ROW_FORMAT=DYNAMIC;
ALTER TABLE housekeeping ROW_FORMAT=DYNAMIC;
ALTER TABLE inputgroup ROW_FORMAT=DYNAMIC;
ALTER TABLE internetcontent ROW_FORMAT=DYNAMIC;
ALTER TABLE internetcontentarticles ROW_FORMAT=DYNAMIC;
ALTER TABLE inuseprograms ROW_FORMAT=DYNAMIC;
ALTER TABLE iptv_channel ROW_FORMAT=DYNAMIC;
ALTER TABLE jobqueue ROW_FORMAT=DYNAMIC;
ALTER TABLE jumppoints ROW_FORMAT=DYNAMIC;
ALTER TABLE keybindings ROW_FORMAT=DYNAMIC;
ALTER TABLE keyword ROW_FORMAT=DYNAMIC;
ALTER TABLE livestream ROW_FORMAT=DYNAMIC;
ALTER TABLE logging ROW_FORMAT=DYNAMIC;
ALTER TABLE music_albumart ROW_FORMAT=DYNAMIC;
ALTER TABLE music_albums ROW_FORMAT=DYNAMIC;
ALTER TABLE music_artists ROW_FORMAT=DYNAMIC;
ALTER TABLE music_directories ROW_FORMAT=DYNAMIC;
ALTER TABLE music_genres ROW_FORMAT=DYNAMIC;
ALTER TABLE music_playlists ROW_FORMAT=DYNAMIC;
ALTER TABLE music_radios ROW_FORMAT=DYNAMIC;
ALTER TABLE music_smartplaylist_categories ROW_FORMAT=DYNAMIC;
ALTER TABLE music_smartplaylist_items ROW_FORMAT=DYNAMIC;
ALTER TABLE music_smartplaylists ROW_FORMAT=DYNAMIC;
ALTER TABLE music_songs ROW_FORMAT=DYNAMIC;
ALTER TABLE music_stats ROW_FORMAT=DYNAMIC;
ALTER TABLE music_streams ROW_FORMAT=DYNAMIC;
ALTER TABLE mythlog ROW_FORMAT=DYNAMIC;
ALTER TABLE mythweb_sessions ROW_FORMAT=DYNAMIC;
ALTER TABLE networkiconmap ROW_FORMAT=DYNAMIC;
ALTER TABLE oldfind ROW_FORMAT=DYNAMIC;
ALTER TABLE oldprogram ROW_FORMAT=DYNAMIC;
ALTER TABLE oldrecorded ROW_FORMAT=DYNAMIC;
ALTER TABLE people ROW_FORMAT=DYNAMIC;
ALTER TABLE phonecallhistory ROW_FORMAT=DYNAMIC;
ALTER TABLE phonedirectory ROW_FORMAT=DYNAMIC;
ALTER TABLE pidcache ROW_FORMAT=DYNAMIC;
ALTER TABLE playgroup ROW_FORMAT=DYNAMIC;
ALTER TABLE powerpriority ROW_FORMAT=DYNAMIC;
ALTER TABLE profilegroups ROW_FORMAT=DYNAMIC;
ALTER TABLE program ROW_FORMAT=DYNAMIC;
ALTER TABLE programgenres ROW_FORMAT=DYNAMIC;
ALTER TABLE programrating ROW_FORMAT=DYNAMIC;
ALTER TABLE recgrouppassword ROW_FORMAT=DYNAMIC;
ALTER TABLE recgroups ROW_FORMAT=DYNAMIC;
ALTER TABLE record ROW_FORMAT=DYNAMIC;
ALTER TABLE record_tmp ROW_FORMAT=DYNAMIC;
ALTER TABLE recorded ROW_FORMAT=DYNAMIC;
ALTER TABLE recordedartwork ROW_FORMAT=DYNAMIC;
ALTER TABLE recordedcredits ROW_FORMAT=DYNAMIC;
ALTER TABLE recordedfile ROW_FORMAT=DYNAMIC;
ALTER TABLE recordedmarkup ROW_FORMAT=DYNAMIC;
ALTER TABLE recordedprogram ROW_FORMAT=DYNAMIC;
ALTER TABLE recordedrating ROW_FORMAT=DYNAMIC;
ALTER TABLE recordedseek ROW_FORMAT=DYNAMIC;
ALTER TABLE recordfilter ROW_FORMAT=DYNAMIC;
ALTER TABLE recordingprofiles ROW_FORMAT=DYNAMIC;
ALTER TABLE recordmatch ROW_FORMAT=DYNAMIC;
ALTER TABLE scannerfile ROW_FORMAT=DYNAMIC;
ALTER TABLE scannerpath ROW_FORMAT=DYNAMIC;
ALTER TABLE schemalock ROW_FORMAT=DYNAMIC;
ALTER TABLE settings ROW_FORMAT=DYNAMIC;
ALTER TABLE storagegroup ROW_FORMAT=DYNAMIC;
ALTER TABLE tvchain ROW_FORMAT=DYNAMIC;
ALTER TABLE tvosdmenu ROW_FORMAT=DYNAMIC;
ALTER TABLE upnpmedia ROW_FORMAT=DYNAMIC;
ALTER TABLE user_permissions ROW_FORMAT=DYNAMIC;
ALTER TABLE user_sessions ROW_FORMAT=DYNAMIC;
ALTER TABLE users ROW_FORMAT=DYNAMIC;
ALTER TABLE videocast ROW_FORMAT=DYNAMIC;
ALTER TABLE videocategory ROW_FORMAT=DYNAMIC;
ALTER TABLE videocollection ROW_FORMAT=DYNAMIC;
ALTER TABLE videocountry ROW_FORMAT=DYNAMIC;
ALTER TABLE videogenre ROW_FORMAT=DYNAMIC;
ALTER TABLE videometadata ROW_FORMAT=DYNAMIC;
ALTER TABLE videometadatacast ROW_FORMAT=DYNAMIC;
ALTER TABLE videometadatacountry ROW_FORMAT=DYNAMIC;
ALTER TABLE videometadatagenre ROW_FORMAT=DYNAMIC;
ALTER TABLE videopart ROW_FORMAT=DYNAMIC;
ALTER TABLE videopathinfo ROW_FORMAT=DYNAMIC;
ALTER TABLE videosource ROW_FORMAT=DYNAMIC;
ALTER TABLE videotypes ROW_FORMAT=DYNAMIC;
ALTER TABLE weatherdatalayout ROW_FORMAT=DYNAMIC;
ALTER TABLE weatherscreens ROW_FORMAT=DYNAMIC;
ALTER TABLE weathersourcesettings ROW_FORMAT=DYNAMIC;

and then ran it like this:

mysql -umythtv -pPassword1 mythconverg < alter_tables.sql