Last of the Summer Wine: Series 21

Season overview

Role: Meticulous television and film archivist.
Task: Produce a JSON object for "Last of the Summer Wine" Season 21.
Constraints:
Use ONLY provided SYNOPSIS and SOURCES.
No invented titles, names, dates, counts, awards, ratings, etc.
If a detail is missing, omit it.
Output: Valid JSON only (no markdown).
Keys: overview (160-220 words), primer (array of exactly 4 concise bullet points).
Style: Original, neutral, encyclopedic prose, plain text.
TMDB Season Synopsis:
The trio in this series consisted of:
Compo only appeared in the Special and the first three episodes of this series prior to his death.
Tom only appeared in four episodes of this series and became a supporting character from series 22 till the shows end.
Source [1]: Longest running comedy series. Three senior citizens unencumbered by wives, jobs, or responsibilities.
Source [2]: Cast and crew credits info (no specific plot/character details for S21).
Source [3]: British sitcom set in Yorkshire, created/written by Roy Clarke, BBC 1973-2010.
Source [4]: They spend days speculating about townsfolk and thinking up adventures not usually favored by the elderly. Premiered 1973. 295 episodes total.
Source [5]: Affectionate comedy about people in the autumn of their years. World's longest-running sitcom, over 30 series and Christmas specials.
Overview:
Goal: 160-220 words.
Content: Season 21 involves a trio of characters. Compo appears in the Special and the first three episodes before his death. Tom appears in four episodes of this series and transitions to a supporting character starting in series 22. The series follows senior citizens unencumbered by wives, jobs, or other responsibilities. These characters spend their days speculating about fellow townsfolk and engaging in adventures not typically favored by the elderly. Set in Yorkshire, the show is a British sitcom created by Roy Clarke.
Drafting (Mental Check): I need to hit 160-220 words. The provided text is very sparse.
Problem: The provided text for Season 21 is extremely limited. It only mentions Compo's death and Tom's appearance count.