There are many tipping points, and we dont always know if we’ve hit one yet or not. The drastic increase in sea temperature the last two years is possibly a tipping point we’ve passed, esp since the warmer the water is, the less co2 its able to absorb. OMAC shut down (if it happens) is possibly a tipping point, which will only feedback loop into warming waters.
Honestly, the permafrost melt is more likely to be the KO punch after one or more other tipping points accelerate it.
For an open source solution, DivestOS’s Carrion is probably the best bet. There are a few others kicking around f-droid as well.
https://gitlab.com/divested-mobile/carrion
I haven’t used it, but I’ve heard good things about it and I enjoy many of their other apps. I too just use the google pixel blocker because its way too good.