Hey, nice to know GJC Web Design,
Thank you. I am not alone

I even set up a new server thinking it must have been at my end after failing multiple > J! 4 upgrade attempts (rolled back from MariaDB and things like that).
Figured I must have had an incompatible plugin somewhere so decided to strip things back and add one by one... But this kept popping up…
As Jumbo points out in your link above, “The issue is created by the jQuery Chosen library being loaded by your template. If you switch to any other template, the problem will be resolved.”
I haven’t added any templates… The only stuff in my build is what comes in the VirtueMart4.0.0_Joomla_3.10.8-Stable-Full_Package.zip package and the admin state drop down breaks when I upgrade this install to J! 4. Same situation when launching fresh J! 4 builds.
Thankfully I have a backup and might hold at Joomla! 3.10.9 / VirtueMart 4.0.2 10661 for a while.
I only post once a year and you’re generally the guy who answers.
Many thanks and have a great one.