The last stable releases for both ARM and MIPS versions are:

2021.5 - 14th August, 2021

2021.4 - 16th June, 2021 (MIPS RT-AC and SDK7)

2021.3 - 05th June, 2021

2021.2 - 28th March, 2021

2021.1 - 20th February, 2021

2020.8 - 19th December, 2020

2020.7 - 01st October, 2020 (MIPS RT-AC only)

2020.6 - 25th September, 2020

2020.5 - 17th July, 2020

2020.4 - 10th July, 2020

2020.3 - 9th May, 2020

2020.2 - 20th March, 2020