Should work.
Look through /var/log/Xorg.0.log to see if the second monitor is detected by the RX560 and the linux drivers. You should see a line that says “EDID for output DVI-0” and a line with “EDID for output HDMI-0”. The next line after the EDID line should be you monitors model info. There are lines for your monitors capabilities, etc.
You can also look through the same log file on you PIs and the Linux mint machine to see what the monitor should be sending.
djb