There seems enough competitors when this looks like a tool from 20 years ago with limited functionality.
If you somehow do not use the obvious GUI tools like TablePlus, Postico or SequelAce but prefer web based, there are some that actually look modern.
https://www.getmotoradmin.com/
For readonly usage, Redash and Metabase are good.
This perhaps misses the point: the beauty of Adminer is that it works as a single PHP file that you can deploy in a shared hosting environment.
While the other linked tools are really cool, they have completely different goals: a low-code/no-code approach to working with data, instead of managing a MySQL/MariaDB instance when you don't have access to the DB server, the server refuses "remote" connections, you don't have SSH access for tunneling or want to do management through a web based interface instead of something like DataGrip, MySQL Workbench or even the CLI.
Though if someone really liked Motor Admin or NocoDB, there are a lot of great (self-hostable) Airtable alternatives out there as well, some of which are listed here: https://alternativeto.net/software/airtable/?platform=self-h...
I could have sworn that there was another list on GitHub of similar tools as well, in the style of https://github.com/awesome-selfhosted/awesome-selfhosted though.