Fix your heart rate zones in Strava
Strava will file your easy runs as threshold for months and you probably will not notice, because it guesses your max heart rate off your age unless you tell it otherwise. Mine is 205 and the guess was about 188.
Settings → My Performance, set your max heart rate to a number you have actually seen on a chest strap, and turn on Heart Rate Reserve if your resting HR is low. Strava recalculates your whole history right away, which is either satisfying or mildly upsetting depending on what it finds.
The steps
Why the default is wrong for a lot of people
220 minus your age is a population average with something like 10 to 12 bpm of spread either side, so a fair number of people are probably 20 off it in one direction or the other. I'm in my early thirties, I go from 43 asleep to 205 running, and no calculator was ever going to produce that.
I don't think the cost of this is cosmetic either. If your zones are set 17 bpm too low, everything you do reads one zone too hard, so your genuinely easy runs come back labeled tempo, your weekly intensity distribution looks like you're crushing it, and you have no idea you're doing the moderate-every-day thing until something hurts.
Getting a real max
Use a chest strap and take the highest number you have actually seen at the end of a hard hill rep or the last minute of a race. Not a calculator, and not your wrist sensor, which undercounts badly at the top end because optical readings drift when your arm is tense and your cadence is high, which is exactly when you are near max.
Also worth knowing your max seems to be a bit lower on the bike than running, usually by something like five to ten beats, so if you do both you want two numbers rather than one. Strava only holds one, which is a limitation you just have to live with (I set mine off running and accept that cycling zones read slightly hot).