Just going by what the Bible says.
The context of Hebrews 3 carries into Hebrews 4. The example of disobedience are those who didn't enter God's rest due to unbelief and disobedience to a literal 7th day Sabbath.
This becomes more evident in Hebrews 4:8 when it's said that if Joshua, a mere human, would have given them rest then God wouldn't have spoken about another day. Humans can't give other humans eternal rest, but they can mark a calendar day off and set it aside as a day of rest. Therefore, the day of rest that isn't believed in is a literal calendar day that someone like Joshua could have given his people.
Hebrews 4:8
8For if Joshua had given them rest, God would not have spoken later about another day.
That this is a literal day that we have to observe is further evident in the context. It isn't God who is giving them rest, but rather they are taking their rest in God's rest, otherwise there would be no need to make every effort to enter the rest.
Hebrews 4
9There remains, then, a Sabbath-rest for the people of God;
10for anyone who enters God’s rest also rests from their works, just as God did from his.
11Let us, therefore,
make every effort to enter that rest, so that no one will
perish by following their example of disobedience.
The perishing via disobedience mentioned are those people in the wilderness for 40 years talked about in Hebrews 3 who were unbelievers and disobedient to the Sabbath:
Hebrews 3
16Who were they who
heard and rebelled? Were they not all those Moses led out of Egypt?
17And with whom was he angry for forty years? Was it not with
those who sinned, whose bodies perished in the wilderness?
18And to whom did God swear that they would never enter his rest if not to
those who disobeyed? 19So we
see that they were not able to enter, because of their unbelief.
So since this is about a literal day and people not entering in due to unbelief and disobedience, would you say you are also not a believer in the Sabbath and also disobedient to it?