I had times where the android Not Chrome would freeze on my phone. I turned off an extension that adds a panel for more buttons and the freezes disappeared. Idk if this will be relevant to your problem since it's your whole phone that froze but maybe you're using some problematic extensions or you may have had some settings that caused it.
Libretube would have replaced the youtube app for me if not for how slow their instances are for me. So far I did not see any crashes but the pages would sometimes not load and would require you to change instances. I think the cause may have been that the instances are hosted far away from me geographically and that my current internet connection has been having issues for non-mainstream websites.
The other day, a place in the Philippines recorded a Heat Index of around 58 degrees Celsius (136 F). That is classified as Extreme Danger and most places have heat index a little bit lower than that.
I did not dropped reddit completely, occasionally going in there through google searches but ever since the api fiasco I've never visited the site directly. I still haven't deleted my account but didn't used it since then and is planning to delete it. Lemmy does not have a lot of content and the niche communities compared to reddit. That is not a bad thing though and instead it had stopped me from mindless scrolling I picked up from using reddit.
I had times where the android Not Chrome would freeze on my phone. I turned off an extension that adds a panel for more buttons and the freezes disappeared. Idk if this will be relevant to your problem since it's your whole phone that froze but maybe you're using some problematic extensions or you may have had some settings that caused it.