It appears that AstroRelay arc builds are not available (yet?) for Flint GL-AX1800, at least it does not show up in the list of routers in the AstroRelay agent settings page, and I can’t see compatible binaries in Index of /download/OpenWRT/ either.
Do you by chance have a valid version for 21.02 GoldenOrb on GL-AP1300LTE? I tried the A7 cortex 2102 version, but shows as incompatible. I believe this is an ARM Cortex A7 Neon in this thing.
There’s a couple available at astrorelay.com
arc_1.0.0-qsdk11_0_ipq.ipk
arc_1.0.0-qsdk5_3_ipq.ipk
I’ve tried multiple links to other A7 cortex ipk files to no avail, each time it shows incompatible architecture.