first, the deadline to obtain a refund for the 2018 tax year was April 15, 2022. if you file expecting a refund, it will be rejected by the IRS.
If you owe money, then you still need to file - there is no deadline in that instance.
best bet would be to ask a paid preparer who would still have access to the appropriate software to file your federal and state income tax forms.
If you want to use the forms and prepare 2018 by hand, you can do that. If the form shows a refund you will not receive the refund; the refund has been forfeited because it is too late.
If you owe taxes, the interest/penalties will be calculated by the IRS based on how much you owe and when they receive your return and payment. The IRS will bill you for this.
2018 Form 1040, Schedules and Instructions
https://www.irs.gov/pub/irs-prior/f1040--2018.pdf
https://www.irs.gov/pub/irs-prior/i1040gi--2018.pdf
2018 Tax and EIC Tables https://www.irs.gov/pub/irs-prior/i1040tt--2018.pdf
IRS 2018 Schedules 1 thru 6 (only if needed)
Sch 1 : https://www.irs.gov/pub/irs-prior/f1040s1--2018.pdf
Sch 2 : https://www.irs.gov/pub/irs-prior/f1040s2--2018.pdf
Sch 3 : https://www.irs.gov/pub/irs-prior/f1040s3--2018.pdf
Sch 4 : https://www.irs.gov/pub/irs-prior/f1040s4--2018.pdf
Sch 5 : https://www.irs.gov/pub/irs-prior/f1040s5--2018.pdf
Sch 6 : https://www.irs.gov/pub/irs-prior/f1040s6--2018.pdf
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