You need to find the type of RC receiver on the plane, and the protocols it speaks, and the type of radio/transmitter you have, and the protocols it speaks. A common controller/radio/transmitter brand is FrSky with the ACCST protocol (apparently now ACCESS), Flysky with AFHDS2A, and Spektrum with DSMX. Each of these brands and protocols has their own binding procedure described in the transmitter and receiver manuals. Since this article is about inexpensive, the least expensive, well-known brand I listed here is Flysky. Frsky is more about open source and modularity, and Spektrum is the most American but not cheap or open. Radiolink appears to be another large brand but I don't know as much about them.
Generally, all of these are about sending a PWM signal, with the pulse width being 1.0 ms - 2.0 ms, where 1.5 ms is the "center" position, at an update rate of 50 hz, to represent the controller stick positions, with 4 channels, two for each axis of two sticks, and perhaps additional channels for communicating more data from a fancier controller to a fancier receiver for things like flaps, landing gear, flight modes, etc.
I don't really see what FrSky did as shady - they introduced a new system with DRM that was not compatible with their old system, which was widely cloned. They did a really poor job at communicating these changes and explaining the implications, but I don't feel that there was anything malicious about it - just a matter of poor documentation. Their main competitor at the time (TBS) also has extensive DRM on their system, they just haven't yet had to deal with 1:1 clones.
Anyway, you're right that ExpressLRS appeared to eat their lunch, especially now that it's approaching legality in many regulatory regions. ELRS is really a very strong open source story - a hack project appeared out of nowhere and managed to disrupt a whole cottage industry by virtue of being community built and supporting a wide range of implementations.
The shady part was not them releasing their new ACCESS system. But releasing stupid "critical" (not really) firmware updates to their ACCST 1.x systems, that were backwards incompatible with their own systems. At one point users couldn't even find the older firmware for their own hardware, and had to download it from 3rd party backups on Google drive etc.
It seemed like they always took that one extra step to make life more miserable to their own users. Inverted ports for sbus (that were a pain for telemetry on F4 processors). Kept releasing so many protocols (D8, ACCST 1.x, ACCST 2.x, R9, R9 2019) and new hardware that didn't work well with their own older hardware, just to stick it to "1:1 clones"?
I used to help out a lot of newbies with this hobby and half the issues I have had to help them with were just the Frsky compatibility issues.
You'd need a really strong reason to not use ExpressLRS, especially when coming in new. The Wifi flashing, binding phrase, "power pellet" receivers, and (in ELRS 3) Wifi-connected Betaflight (no more USB!), are space age technology compared to the previous generation.
Generally, all of these are about sending a PWM signal, with the pulse width being 1.0 ms - 2.0 ms, where 1.5 ms is the "center" position, at an update rate of 50 hz, to represent the controller stick positions, with 4 channels, two for each axis of two sticks, and perhaps additional channels for communicating more data from a fancier controller to a fancier receiver for things like flaps, landing gear, flight modes, etc.