Customizer always crashes

Hi thanks for the suggestion. I installed 2021 and now things are working okay.
Reactivated all the plugins and just crashed once after activating UpdraftPlus.
2021 is doing the trick for now. But for how long?

I see. Thank you for testing. If it still crashed with twenty twenty one theme activated, even once, then the issue is not theme related. That is, it's likely that it will occur with any theme, even WordPress default themes. It shouldn't crash as well when activating or deactivating a plugin.

I would suggest to try testing with a different device and check if the issue is device isolated. It would also be good to start a staging site to do your tests.

To reiterate, the Customizer shouldn't cause a crash. Nor, does activating or deactivating a plugin. The next best step is ask your hosting provider for insights with regards to this.

Hope this helps!