Kinda fun fact about that.
When your google account is enrolled in advanced protection, you can't install sideloaded apps. BUT, you can update them. So if you installed one before enabling it or installed one using a computer, you can update it as normal on the phone.
If you enable advanced protection on the phone or auto blocker, you cannot update sideloaded apps.
So for me having some sideloaded apps, I disable auto blocker and advanced protection on the phone, update the app, turn them back on.
To install a brand new app, I need to either disable it on my account or use my pc and adb