Ven. Yuttadhammo, who was formerly a moderator of Buddhism.SE, heads the Sirimangalo International Meditation Centre in Ontario, Canada. He was a student of Ven. Ajaan Tong Sirimangalo.
He teaches vipassana meditation, which is very beneficial.
You can find his meditation e-books online:
How to Meditate
How to Meditate II
The "How to Meditate" e-...
For students who have already done a course one can use the mobile app: Dhamma.org Mobile App.
Also, some centres have organised online group sittings for old students: https://pamoda.dhamma.org/en/os-vipassana/online-group-sits/
There’s a lot of vague opinion here. Several studies have shown at as little as 20 mins (two 10 minute sittings) a day is sufficient to receive benefits. In fact this level of practice is the basis of one of the most popular book-based Mindfulness courses in the world (Mindfulness: A Practical Guide to Finding Peace in a Frantic World).
This book is ...