Maybe try force closing and restarting the app. I don't remember how long it took boinc to load first time on android, but don't remember it taking too long.

I had this issue on Pine A64s. I had to update Android System WebView or something like that in the play store, that solved the problem.

Boinc shouldn't take more than a few seconds to load, so if it hangs for minutes/an hour it's not going to work.

Perhaps this link can give a bit of insight: https://boinc.berkeley.edu/dev/forum_thread.php?id=11286 I believe the suggestion was to attempt using an older version which you can find on Berkeley's page. I know that thread talked about the x86 version, but it may apply to both x86 and ARM devices.

Edit: Berkeley's page https://boinc.berkeley.edu/download_all.php