Yes, this file essentially used to run commands on startup. Without an entry made by user (as you have added 2 lines), it does nothing.
An alternative way to run the startup files is to add these to cron job.
(a) Give command: sudo crontab -e
(b) In file opened, scroll down and at bottom add following lines:
@reboot /bin/bash /usr/local/share/adsbexchange/adsbexchange-feed.sh &
@reboot /bin/bash /usr/local/share/adsbexchange/adsbexchange-mlat.sh &
(2) After completing above step, Reboot Computer to start adsbexchange scripts.
MX-Linux is shipped with systemd builtin, with options to boot either with or without systemd enabled. By default, it boots without systemd disabled. This can be changed in Grub settings to make boot with systemd enabled as default.
Most software packages now a days use systemd. What is wrong in running MX-Linux with systemd enabled?