Yes you can apply in those 3 countries and many more. Success stories will be in the threads. You were misinformed about applying only from your home country as evidenced by the success stories in this group.
Taipei- same day in person approval. Now it is 2 -3 days online with an interview likely needed and for Soft Power you must provide employment documentation. I would say Jakarta, Vietnam and Manilla are "easier " , with approvals around 3-5 days. Tiger Eye is a well-known DTV approved Gym in Bangkok, Muay Thai Fever reputable gym in Chiang Mai.
That's great Tokyo has now dropped its' restrictions on permanent residents. Also the application seems easier than before. When I looked at applying in Tokyo last year, you needed a guarantor, 6 months accommodation booked in Thailand. A recent successful Tokyo applicant noted it is better to apply elsewhere than Tokyo if you have an option. His post should be in the threads.
Anonymous participant You are not showing you are living in Vietnam only that you are staying while your application is processed. Some embassies disprove of short term Airbnbs for long term residency evidence, you are not living in Vietnam just making an application. It is not a problem using an Airbnb to apply for the DTV, other applicants have used the same and similar platforms. Show the duration of the time you intend to stay in Vietnam. 5 business days is average for Vietnam so a bit more than that should be suffice.
There was a post by a successful Tokyo DTV applicant who had an interview. Essentially they want to clarify what you have documented. Bring your paperwork and just be ready for some questions.