Yes I swear I've tried over 20 times to set a custom ttf font. With mono and with zfont. I've tried all different ways to get this to work. But I think like @sathishtony said since Samsung cloud resets to default font I can never get this to work on Android 11 with my s20. I'm so bummed because I can't even use a custom font with my launcher (Total Launcher) anymore because of the Android 11 update. I wish I could go back to Android 10 when everything worked. Well at least some ppl are able to take advantage of this awesome find/opportunity.
Did you debloaded or disable Samsung apps???? I am using S20+ also. Took me 2 days to figure it out because of Debloaded Samsung apps. 1st, you MUST to enable all the apps back. Then redo again. After you got your FAV.ttf installed, then you can disable all the samsung apps. I worked for me.