No, it is too late to file an extension for tax year 2023 and tax year 2024. File your 2023 taxes as soon as you can. Here is a link to get started with your 2023 tax return using the desktop software.
Sorry, Online is only for 2024 now. Online for 2023 and prior is closed now so you can not start a new 2023 or prior return or finish one. You have to do each year separately
How to prepare a prior year return
https://ttlc.intuit.com/community/using-turbotax/help/how-do-i-prepare-a-prior-year-tax-return/00/25984
To do a prior year return you have to buy the Desktop program here,
https://turbotax.intuit.com/personal-taxes/past-years-products
You will need a full Windows or Mac to install it on.
If you have a simple return and want to file for free you can fill out the forms by hand. Here are some basic forms…..
Here is the IRS 2023 Form 1040
https://www.irs.gov/pub/irs-prior/f1040--2023.pdf
or if you want bigger type use 1040SR for Seniors,
https://www.irs.gov/pub/irs-prior/f1040s--2023.pdf
And 2023 Instructions
https://www.irs.gov/pub/irs-prior/i1040gi--2023.pdf
2023 Tax and EIC Tables
https://www.irs.gov/pub/irs-prior/i1040tt--2023.pdf
Sch 1 : https://www.irs.gov/pub/irs-prior/f1040s1--2023.pdf
Sch 2 : https://www.irs.gov/pub/irs-prior/f1040s2--2023.pdf
Sch 3 : https://www.irs.gov/pub/irs-prior/f1040s3--2023.pdf
Then when you do file 2024 enter 0 for the 2023 AGI since you are filing 2023 late.
You have to print and mail prior year returns. When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s. Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS received the return. Don’t forget state.
If you do not owe or will get a refund for 2023, there is no penalty for filing late. If you owe tax due, your late filing penalties and interest have been adding up since last year's filing deadline, so get it mailed asap with your payment of the tax due as shown on the tax return and then expect a bill for the additional amount you will owe. You have also missed the chance to request an extension for 2024, so the same advice applies.
You can only file 2023 by mail. 2024 can be e-filed, but you will need to use "zero" as your AGI when you try to e-file 2024, since the IRS will not have a 2023 AGI in the system for you.