Ok, this was super silly resolution.

I had wrong CE pin selected, and confusion bit me again on the pin vs gpio thing of the header/brcm gpio mapping.

On my rf24 module, I had (from previous implementations) wired up CE to GPIO 22 (pin 15), and IRQ to GPIO 25 (pin 22). So default CE line for rpi/rf24/mysgw is "22" (pin, NOT gpio ;)

The frustration was that my module was being recognized, which gave false appearance of complete wiring correctness, but I think it never transitioned to TX.
Not sure if it would be possible to sanity check RF24 driver to verify if CE line is working in module wiring or not.

Anyhow, moral of the story is to check and double-check the wiring!!!

I also found the logparser did not handle certain log entries, such as the logfile produced by the mysensors gateway on raspberry pi, e.g. prefixed with timestamps, etc.

Opened pull request to improve this, comments welcome, especially if you are able to test this locally (only need to copy the Logparser directory and open logparser.html locally in a browser):
https://github.com/mysensors/MySensors/pull/1468

Great Scott! channel did a few great videos on this:
https://www.youtube.com/watch?v=pGLUsQozT94
https://www.youtube.com/watch?v=h8ycmroFQSs

(I have been using cheap clear nail polish from dollar store, and it seems like it works for moisture protection... not using for submersion however.)

@magpern

for others trying to find a good channel, I found this useful showing Wifi and BLE channels. (Orange are BLE advertising channels, which should always be reserved/unoccupied by NRF stuff):

Yes I think wifi channels >11 (like 12,13,14 overlap to 2476).
So sometimes nrf channel 1 is a good choice, but as always, depends on your environment ;)
Do you have wireless mice, keyboards, etc - many of these use NRF24 or similar 2.4GHz ISM? Are you sure the other 2.4GHz devices are really bluetooth and not proprietary?

@Dreded
FWIW, I don't have direct experience myself with longevity and durability of heatshrink + hot glue, but one of the YT channels I follow does. Julian Ilett has a custom-built pwm solar charge controller which he made small production runs of, and started having failure issues with this method, as these are exposed to outdoor environmental conditions.
https://www.youtube.com/watch?v=_YGlRkArsyA

however, I would think that "potting" or filling the heatshrink openings with "RTV" (i.e. room-temperature vulcanizing) silicone sealant. This stuff is used on marine and aircraft applications to completely waterproof stuff.