On my Subscribed view on lemm.ee sorted by Hot which very recently upgraded lemmy-ui to 0.19.4 (your lemmy.sdf.org instance has not upgraded yet, just checked), of 14x news items/links which should have thumbnails - 8x of them are broken/missing, just over 50%.
Might I recommend https://liberapay.com/ ? As a user, I can donate with PayPal and they minimize vendor fees by collecting up front from me and performing recurring donations to you (lemm.ee) and it allows me to retain personal privacy if so desired (per the other reply). Here is the core Lemmy developer using the platform for example: https://liberapay.com/dessalines/ | https://liberapay.com/Lemmy/