I couldn't find any information on the amount of Flash/RAM the router has except for one website, https://www.batna24.com/en/p/tplink-archer-c54-wifi-router-rmmjj , which states that the router allegedly has 64 MB of RAM, so I presume that Flash may have 8 MB in this case.
The question is, can this specific device be supported by OpenWrt, and if so, by which time (rough approximation, e.g. Q3 of 2021, etc.) it will be developed?
The OEM firmware image is 2.1 MB in size, which suggests 4 MB flash and probably non-linux for the OEM firmware. The remaining technical specifications don't win any beauty pageants either, nor does its price - just skip this $thing and get something decent.