even with the "linux" version of ventoy , the main partition where iso's are dropped is exfatYour first picture shows that the USB stick is formatted to exfat. Did you do this, or did Ventoy do it?
exfat needs some extra bits to make it readable.
sudo apt install exfat-fuse exfat-utils
Except the OP's 1st photo only shows Partition 1 (513 MB) as exfat (not large enough to hold any .iso files). Partition 2 is an "unknown" filesystem.... suggesting (to me) that it was never created properly, or was deleted, or was corrupted.even with the "linux" version of ventoy , the main partition where iso's are dropped is exfat