If you record heart rate, you know your maximum, rest, and threshold (LT) heart rate for this kind of activity, and post these activities on Strava, you can use the Elevate extension to calculate its “HRSS”, which is more or less the same as hrTSS.
HRSS is computed from TRIMP.
HRSS_activity = (TRIMP_activity) / (TRIMP of one hour at LTHR)
TRIMP = sum( dt * HRR * 0.64 * exp(k * HRR) )
HRR = (HR - HR_rest) / (HR_max - HR_rest)
k = 1.92 for men, k = 1.67 for women