Well, a wemos D1 only has 1 AnalogInput, so you would only be able to connect one eTape, as long as you do not multiplex that.
Looks like Tasmota works on certain ESP32 chips as well though. There you would have 6 Analog Inputs and more than enough pins for everything. Tasmota does also support counters (for the flowmeters) and I2C, so it looks doable if you want to do it that way.
That does of course mean that you will probably not have a ReefPi controller, but well, I'm not one to judge ^^
There are a couple of "scriptable device" firmware packages in the ESP/Home Assistant/MQTT universe, which makes building these things easier especially from a pure monitoring POV. Tasmota is one, as is https://esphome.io/ . I don't have much opinion/experience with either, but its a pretty quick way to get things setup - honestly, getting HA running is probably harder just because its Python ecosystem is very brittle.
Yes, this isn't Reef-Pi, but can absolutely still be hooked to it (or HA, or things of your choosing).