I had issues with esimx eSIM (Japan-only plan). It activated successfully but did not connect to any network.
It turns out you need to add APN manually. For esimx it's "3gnet".
After that, the network instantly connected to KDDI LTE. Softbank also works (but KDDI is "native" for this SIM, while Softbank is "roaming").
That's with Pixel 8a.
P.S. for anyone wondering, I would NOT recommend this eSIM. It routes the internet via Hong Kong (and you get Hong Kong IP address) with pretty low speed. However this is the cheapest plan I found (20 GB for 30 days for $16).