Many consider LTHR a better way of calulating your zones. Using HRmax is more generic; 2 people with a HRmax of 190 could have very different HR’s at threshold.
I’ve calculated mine in TP based on LTHR using the Coggan method.
This is a good article explaining how to estimate your LTHR:
Determine your lactate threshold heart rate (LTHR) with a short test. (Do not use 220 minus your age to find max heart rate as this is as likely to be wrong as right.) This LTHR test is best done early in the Base and Build periods.
To find your LTHR do a 30-minute time trial all by yourself (no training partners and not in a race). Again, it should be done as if it was a race for the entire 30 minutes . But at 10 minutes into the test, click the lap button on your heart rate monitor. When done, look to see what your average heart rate was for the last 20 minutes. That number is an approximation of your LTHR.