External Sharing with Non-MS Accounts (Verification Codes)

Hello! I was wondering if anyone has guidance for the following conundrum...

I’m trying to share some files and folders with external clients. I was going to create guest accounts and add them from a group from there but they are restricted from creating Microsoft accounts (on their end). I’ve landed on sharing a one-time verification code to access files and folders, and extending code authentication timelines out 100 days (so it’s not a nuisance reverifying every time they access a file). Would persistent cookies need to be enabled to ensure their codes aren’t wiped clean every couple of days? Does anyone know of a better way to share files for collaboration with external users that do not have MS accounts?

Thank you so much