On Reddit:
https://www.reddit.com/r/apexlegends/comments/ancth2/a_large_portion_of_amd_users_cant_launch_the_game/
"Jayfresh_Respawn: I'm sending this to the team. Sorry for those having issues and I'll send update as soon as I have it."
Nerd Mag:
https://www.thenerdmag.com/apex-legends-is-not-supported-by-amd-phenom/
"This particular AMD phenom processor is actually still capable of handling modern games at decent fps granted that it is supplemented by a decent GPU which in this case is a GTX 1060. it is not certain right now whether EA will release a patch to fix this issue which I think is completely plausible since the issue is not strictly related to the processor itself but the game’s inability to deliver an SSE instruction that is readable by this particular processor."
Gamestar.de (Gamestar is a popular German game magazine/site):
https://www.gamestar.de/artikel/apex-legends-stuerzt-mit-phenom-ii-cpus-ab,3340365.html
"...models with four cores and 3.2 GHz but still have enough power for many current titles, if a halfway current graphics card is in the PC. This also applies to (real) six-cores or some of the cheaper Athlon II X4 models. Also, listed at least AMD FX 4350 or Intel Core i3 6300 (some older Core 2 models from the 7000/8000 series already support SSE 4.1 and therefore should work, contrary to the system requirements anyway) as a minimum requirement.
New games with older CPUs without SSE 4.1 sometimes do not work, this has happened over the years, but sometimes this is fixed by the developers with a patch in retrospect. Apex Legends has not announced a fix for Phenom or Athlon CPUs so far - but the more owners of a corresponding CPU keep reporting it, the more likely this will be."
www.heise.de (another German site):
https://www.heise.de/newsticker/meldung/Apex-Legends-10-Millionen-Spieler-Probleme-mit-aelteren-AMD-Prozessoren-4302368.html
"With regard to the PC version, reports of crashes with processors of the AMD Phenom II, Athlon II or older series rapidly increased in the user forums. These processors do not support the Streaming SIMD Extensions 4.1 (SSE 4.1) extension instruction set used by the game Apex Legends. EA confirmed in the forum that Apex Legends is not running on such processors at the moment. For liquid 60 fps, the developer recommends at least one core i5-3570K, 8 GB of RAM and a GeForce GTX 970 or AMD Radeon R9 290."
(Not sure about you, but my PC destroys that ^ "liquid 60fps" developer recommended spec. Too bad I'm locked out of gameplay).
Some other articles and comments in other languages too, plus @VinceZampella responding on Twitter, looking into it.
STAY FROSTY, STAY HOPEFUL!