Good news: your last 8 weeks already show real trail fitness — 30km long runs, 1450m of vert, hill reps and uphill tempos on repeat. That's not a beginner's base, so I've built a plan that keeps that shape and grows it toward your 50K/2800m day, in Cruise mode (gentle ramps, ~1 quality day/week, a deload roughly every 4th week).
Assumptions I made — tell me if any are off: (1) I kept your Tue/Wed/Fri/Sat run days and put your one weekly strength session on Thursday, since that's your free day and it's never the day before your Saturday long run. (2) Easy pace I've set around 5:50–6:20/km based on your recent easy trail runs. (3) Long run grows from your current ~24-30km toward ~34km peak (about 70% of race distance) by mid/late November, then tapers — never past the 4-5h time cap. (4) Weekly vert climbs toward ~2,600m at peak (roughly your race's D+), with three dedicated downhill sessions (weeks of Nov 2, Nov 16, Nov 30) to blunt quad damage before race day, spaced so the last one lands about 3 weeks out. (5) Race week (Dec 21–27) carries a short uphill sharpener Tue, easy days around it, and openers with strides the day before — never an all-easy taper week, that's what leaves legs flat on race day.
Full detail runs through the next 6 weeks and race week; the weeks between are outlined (same sessions and numbers, shorter descriptions) — I'll sharpen each as it comes into view. Shout if your weekly volume, days, or the 8-hour goal itself need adjusting.