2018 Model 3 RWD owner here. I've had this smell in the past. After the first summer of owning the car, I got the HVAC odors being described here. I did the DIY evaporator cleaner and new OEM filters from my local service center. Smell eventually came back.
This past spring, I did the DIY evaporator cleaner but used a replacement activated cabin filter that I got on Amazon. I used the A/C all spring/summer and the smell has not come back. When using the evaporator cleaner (I used two containers of the 96030 Kool-It), I tried to get as far up the evaporator as I could with the supplied nozzle so that the cleaning foam would slide down as much of the evaporator to clean it. After each canister of cleaner, I would re-install the plastic filter cover over the opening (I didn't need to screw it back in, just press fit) and run the fan for 10 min and made sure the cleaner made it's way out of the car by ensuring the fluid ended up on my garage floor.
Amazon.com: TAPTES Filter for Tesla Model Y Model 3 Replacement Cabin Air Filter 2Pack,Fit for Model Y 2020 2021,for Model 3 2017 2018 2019 2020 2021 : Automotive
These filters seemed loose when I put them in, but it works well to get rid of the odors. One thing I did notice is that the air coming through the vent comes through at a slightly lower speed (think of selecting a fan speed of 6, but actually getting a fan speed of 4 or 5). But I've gotten used to it the air speed and would take this any day over dealing with the HVAC odors. I haven't had to leave the fan running for an extra amount of time or had to shut off the A/C to let the fan run to dry out the evaporator after I drive the car. Now I just leave the A/C setting on to something comfortable (73 degrees for me) and leave it.