I want to practice problems from national olympiads and to get a fell about how the problems are around the world I need your help. I found this site https://olympiads.win.tue.nl/ioi/noi/index.html, but some links are broken or unavailable. If you can shortly describe the process of getting to the national (like are there any regionals) and provide a link it would be very helpful.
I will update the blog with your comments.
Italian training website: training.olinfo.it
In most cases, the path to IOI is local OI -> regional OI -> national OI -> training camps -> IOI.
[Regional OI is tomorrow. Good luck to the participants!]
For Chinese NOI, you could find the problems in https://uoj.ac/problems?search=noi
You can find good portion of national olympiads on Baekjoon Online Judge: national contests
Polish OI website: https://oi.edu.pl/
Problems from previous contests: https://szkopul.edu.pl/p/default/problemset/oi
Australian informatics olympiad: https://www.amt.edu.au/aio
The archive for different australian competitions is on ORAC, there are lots of cool problems there and the website is very nice as well.
Indian OI: https://www.iarcs.org.in/inoi/
Regional Olympiad: ZCO (Zonal Computing Olympiad) Past ZCO Problems There's also an alternative called ZIO (Zonal Informatics Olympiad) which is a written test
National Olympiad: INOI (Indian National Olympiad in Informatics) Past INOI Problems
Training Camp: IOITC (International Olympiad in Informatics Training Camp)
there is a group on cf for previous egyptian ois but some aren't added yet here is the group
Ukraine having NETOI linked on the website you found is hilarious
South African National Olympiad: https://olympiad.org.za/programming-olympiad/past-papers/final-round/