Inspired by @RandomUsagi, I have compiled sources relating to the films (articles, blu-ray, manga, subbers info etc.). 

Official:

Official Film website: https://restart-movie.com/

Announcement article: https://www.crunchyroll.com/anime-news/2020/04/29/cocomis-boys-love-manga-restart-after-come-back-home-gets-live-action-film-this-fall

Announcement article #2: https://psycho-milk.com/2020/05/03/restart-after-come-back-home/

The film's gofund page (Fans had supported the film during the pandemic): https://motion-gallery.net/projects/restart-tadaimanoatode

Blu-ray: YesAsia or CDJapan 

Manga:  Main Manga story  &  Manga Sequel 

Behind the scenes/promotions:

Trailer (with Eng Subs) https://www.youtube.com/watch?v=4qng-GxF9rE

Behind the scenes - https://www.youtube.com/watch?v=-PXj3HArRbU

Interviews:

Ryuusei and Furukawa-san answering what words left an impression by their seniors  - https://www.youtube.com/watch?v=k7MUWJGttnA

The kiss scene discussion - https://www.youtube.com/watch?v=xAL4MgSyiSY

Movie collection Jp interview: https://www.youtube.com/watch?v=4t5u6QurLsY

Horipuro Square interview: https://www.youtube.com/watch?v=EPf_rH8hl1Q

Film info and subber's analysis:

Film Trivia (Character and setting analysis, including Film and Manga comparisons) - Contains Spoilers

https://ichihachiblog.tumblr.com/post/640375998597185536/restart-wa-tadaima-no-atode-film-trivia-updated

Subber's notes (Meaning behind character interactions/dialogue and Japanese culture surrounding the film) - Minor Spoilers 

https://ichihachiblog.tumblr.com/post/640375993775816704/restart-wa-tadaima-no-atode-subbers-notes

May add more updates ^_^

Thank you for all the info! :)